An organic light-emitting diode (OLED) is a luminescence radiator with which electromagnetic radiation is generated from electrical energy. An OLED has at least one organic active layer in which the electromagnetic radiation is generated. The active layer is arranged between an anode and a cathode. On application of a conducting-state potential, the anode injects holes into the active layer, whilst the cathode injects electrons. The injected holes and electrons each move (under the influence of an externally applied electric field) toward the electrode of opposite charge and, on recombination, generate an electroluminescent emission in the active layer.
An electrochromic device typically has a rigid carrier for an active layer which is also embedded between an anode and a cathode. If a DC voltage is applied across the anode and the cathode, a color change takes place in the active layer. For some applications, the anode, cathode and active layer are transparent. Thus the electrochromic layer can, for example, be used as a dazzle protection in a windscreen or a mirror of a motor vehicle.
A problem with such electrooptical devices is that, due to the intrinsic resistance of the anode and/or cathode, a lateral voltage falls off along the respective electrode. The lateral voltage denotes the change of the voltage away from a contact terminal of the electrode (anode or cathode). As a result, an inhomogeneous luminance pattern is formed in, for example, an OLED. In an electrochromic device, an inhomogeneous color pattern is formed. Both effects are undesirable and should be suppressed as far as possible.